Mainframe computers are computers used primarily by large organizatons for critical applications, bulk data processing such as census, industry and consumer statistics, enterprise resource planning (ERP), and transaction processing.
A little trivia
They are colloquially referred to as “big iron.” The term mainframe computers originally referred to the large cabinets called “main frames” that housed the central processing unit (CPU) and main memory of early computers. Later, the term was used to distinguish high-end commercial machines from less powerful units. Most large-scale computer system architectures were estsablished in the 1960s, but continue to evolve.